O'Dea Castle, also known as Dysert O'Dea Castle, is an Irish fortified tower house, loosely described as a castle[1] at Dysert O'Dea (Irish: Dísert, meaning "hermitage"), the former O'Dea clan stronghold, 5 km from Corofin, County Clare just off the R476 road.[2] It was built between 1470 and 1490 by Diarmaid O'Dea, Lord of Cineal Fearmaic, and stands some 50 feet high on a limestone outcrop base measuring 20 feet by 40 feet.[3] The tower is located right next to Dysert O'Dea Monastery.

The castle was built between 1470 and 1490 by Diarmaid O'Dea, Lord of Cineal Fearmaic. The Earl of Ormond took the castle from the O'Dea clan in 1570 by force. By 1584, however, they had regained it. At that time, Domhnall Maol O'Dea was listed as owner. Domhnall supported the northern Chiefs in the Nine Years' War of 1594-1603 and subsequently Dysert Castle fell to the ProtestantBishop of Kildare, Daniel Neylon, who in 1594 bequeathed it to his son, John. The castle soon returned to the O'Dea clan. Conor Cron O'Dea supported the Confederates and participated in the successful siege of Ballyalla Castle in 1642. After the fall of Limerick in 1651 to the Cromwellian forces, they maintained a small garrison here. When they left, the soldiers demolished the battlements, upper floors and staircase. The Neylon family then returned but during the rein of Charles II, Conor Cron O'Dea regained the castle. Conor's sons, Michael and James, supported the cause of James II and once again lost the castle. The lands passed to the Synge family but the castle eventually and gradually fell into ruin.[4]

In 1970, John O'Day of Wisconsin Rapids, WI, USA, purchased the tower and had it restored. The castle was then leased to the Dysert Development Association, which, with support from the Irish Tourist Board, opened it as "The Dysert O'Dea Castle Archaeology Centre" in 1986. It showed an exhibition of local artefacts from the stone age to 1922.[4]

The tower also won the "Clare Tourism Award" for being one of the most authentically rebuilt castles in Ireland.[citation needed]

Today, the centre is known as the Clare Archaeology Centre, with exhibits of local archaeological artefacts from 1000 BC to 1700 AD, local history over the last three centuries, and a wall walk of parts of the castle. The Dysert O'Dea Archeology Trail includes sites around the tower, including the remains of the Dysert O'Dea Monastery.

^Ua Croinin and Breen comment in The Other Clare, 1985: "The castle itself is more correctly designated a tower-house as it falls easily in the category of such fortified houses built in great numbers throughout the southern part of Ireland between 1400 and 1600." (Detailed reference below.)